diff --git a/builder-web.opam b/builder-web.opam
index ba789f8..466827a 100644
--- a/builder-web.opam
+++ b/builder-web.opam
@@ -14,6 +14,8 @@ build: [
 depends: [
   "builder"
   "opium"
+  "bos"
+  "hex"
 ]
 
 synopsis: "Web interface for builder"
diff --git a/lib/builder_web.ml b/lib/builder_web.ml
index 75e268e..4a15f32 100644
--- a/lib/builder_web.ml
+++ b/lib/builder_web.ml
@@ -92,7 +92,7 @@ let routes (t : Model.t) =
           let body = Body.of_string data in
           Response.make ~body ()
           |> Response.add_header ("Content-type", Magic_mime.lookup file)
-          |> Response.set_etag (Base64.encode_string digest.sha256)
+          |> Response.set_etag (Base64.encode_string (Cstruct.to_string digest.sha256))
   in
 
   [
diff --git a/lib/dune b/lib/dune
index ff590ef..7a51a79 100644
--- a/lib/dune
+++ b/lib/dune
@@ -1,3 +1,3 @@
 (library
  (name builder_web)
- (libraries builder opium tyxml bos rresult duration))
+ (libraries builder opium tyxml bos rresult duration hex))
diff --git a/lib/model.ml b/lib/model.ml
index c422c28..529279e 100644
--- a/lib/model.ml
+++ b/lib/model.ml
@@ -25,8 +25,7 @@ type job_run_info = {
 }
 
 type digest = {
-  sha256 : string;
-  sha512 : string;
+  sha256 : Cstruct.t;
 }
 
 type t = {
@@ -59,8 +58,7 @@ let digest (path, data) =
   let module H = Mirage_crypto.Hash in
   let data = Cstruct.of_string data in
   (path, {
-      sha256 = H.SHA256.digest data |> Cstruct.to_string;
-      sha512 = H.SHA512.digest data |> Cstruct.to_string;
+      sha256 = H.SHA256.digest data;
     })
 
 let read_full_with_digests t path run =
diff --git a/lib/model.mli b/lib/model.mli
index 8058aa5..4e69fab 100644
--- a/lib/model.mli
+++ b/lib/model.mli
@@ -9,8 +9,7 @@ type job_run_meta = {
 }
 
 type digest = {
-  sha256 : string;
-  sha512 : string;
+  sha256 : Cstruct.t;
 }
 
 type job_run_info = {
diff --git a/lib/views.ml b/lib/views.ml
index cc49e49..d64fcdf 100644
--- a/lib/views.ml
+++ b/lib/views.ml
@@ -129,17 +129,14 @@ let job_run
       p [txtf "Execution result: %a." Builder.pp_execution_result result];
       h3 [txt "Digests of build artifacts"];
       dl (List.concat_map
-            (fun (path, { Model.sha256; sha512 }) -> [
+            (fun (path, { Model.sha256 }) ->
+               let (`Hex sha256_hex) = Hex.of_cstruct sha256 in
+               [
                  dt [a
                        ~a:[Fmt.kstr a_href "f/%a" Fpath.pp path]
                        [code [txtf "%a" Fpath.pp path]];
                      txt "(SHA256)"];
-                 dd [code [txtf "%s" (Base64.encode_string sha256)]];
-                 dt [a
-                       ~a:[Fmt.kstr a_href "f/%a" Fpath.pp path]
-                       [code [txtf "%a" Fpath.pp path]];
-                     txt "(SHA512)"];
-                 dd [code [txtf "%s" (Base64.encode_string sha512)]];
+                 dd [code [txt sha256_hex]];
                ])
             digests);
       h3 [txt "Job script"];